1. Field Of The Invention
The present invention relates to electrical connectors and, more particularly, is directed toward an improved contact design to be used in modular telephone-style jacks so that during mating, the contact has a bi-directional means of transferring vertical lift by a modular plug into both vertical and horizontal direction.
2. Description Of Related Art
Telephone-style modular jacks are widely used in the computer networking and communications industries for interconnection of computers, modems, printers, and similar electronic equipment.
As utilized herein, the terms "modular jack" and "modular plug" connote the miniature, interchangeable, quick-connect-and-disconnect jacks and plugs developed originally by Western Electric Company and Bell Telephone Laboratories. Examples of modular jacks and modular plugs may be seen as described in U.S. Pat. Nos. 3,699,498: 3,850,497; and 3,860,316.
Various modular jacks have been proposed for directly coupling a modular plug to a printed circuit board. Several designs of modular jacks for this application as described in U.S. Pat. Nos. 4,457,570 and 5,478,261 as well as several of my prior U.S. patents. In U.S. Pat. No. 4,457,570, there is described an improved modular jack that incorporates differential spacing. The principal feature of this improved modular jack is the provision of electrical conductors which enter the plug receiving opening of the jack from the rear of the jack. This provides for a shorter contact length than prior art jacks, resulting in substantial economies from using a reduced amount of costly spring material to make each contact, and reductions in the surface area that must be gold-plated in order to produce a reliable electrical connection between the contact of the jack and the contact in the male plug. While this design is an improvement of prior art designs, it suffers from several deficiencies. This particular design is subject to overstress of one or more contacts when mating with certain types of modular plugs.
The problem of overstress of one or more contacts is inherent in all prior art modular jacks. For example, there are four basic types of modular plugs. They are the four position, six position, eight position, and the ten position. Modular plugs were designed by Bell Telephone Laboratories to have virtually identical physical heights, and to place the releasable latching arm in the center of each plug with the same relative setback dimensions from the nose at the front of the plug, as may be seen in Federal Communications Commission Part 68, National Standards for Telephone Plugs and Jacks. The four types of plugs are essentially identical in their dimensions in the critical inter-mating front portion except that the width of the six position plug is 0.080 inches wider than the four position plug, and the width of the eight and ten position plugs are 0.080 inches wider than the six position plug. This design arrangement permits any plug to be mateably inserted into any jack of the same number position or any jack of a greater number position. For example, this means that a four position plug can be inserted into a four position jack, or a six position jack, or an eight position jack, or a ten position jack. Another example would be that a six position plug could be inserted into a six position jack, or an eight position jack. The consequence of inserting a six position plug is that the six contacts and their respective slots for receiving the corresponding female spring contacts operate exactly as a normal mated connection; however, for the outermost spring contacts, one of either side of the center spring contacts, there is no corresponding contact or receiving slot in the six position plug. When the plug is fully inserted, the outermost spring contacts are lifted to a height approximately 0.023 inches higher than the maximum normal height during mating. Severe stress is exerted against the outermost spring contacts under this mated condition, and the longer the duration of time that the smaller plug remains mated further induces time weighted stress on these outermost contacts. All prior art modular jacks, when subject to mating an eight position jack with a six position modular plug, have at least one outermost spring contact that becomes intermittent after typically only three insertions and remaining in a mated condition for only sixty seconds for each insertion.
U.S. Pat. No. 5,478,261 is designed to address this very serious potential type of field induced failure of a modular jack. An intermediate, transition portion of the contact joins the contact mating portion and joins the solder post portion of the spring contact. The contact mating portion is comprised of several sections: the lower linear beam, the lead-in, the forward tip, and the back angle section. The transition portion of the contact extends typically in a vertical fashion from the solder posts up to a radius directional changer, from which the transition portion typically extends horizontally forwardly toward the front face of the jack. The back angle-up connects to the transition portion and extends downwardly from the transition portion to connect to the lower linear beam. The back angle section enables the lower linear beam to be positioned within the jack so that its beam surface is lower than the horizontal part of the transition portion. The lead-in angles upward from the lower linear beam to the forward tip. The combination of lead-in section with the back angle section makes it possible to locate the mating beam surface relatively far away from the points of flexure for the contact, reducing the effects of the contact being lifted to a high lifted position, the source of excessive stress on the contacts of a modular jack. In addition, the beam surface, when lifted to normal lift height while mated, becomes parallel to the upper surface of the male contact in the plug. This dramatically improves the electrical properties of the connector as will be described hereinafter.
The demand for ever increasing electrical performance for the frequencies that a modular jack can effectively transmit is and continues to drive the need for constant improvement of modular jacks. All prior all jacks fail to deliver most of the signal when delivered at high frequencies such as 100 megabits per second (Mbps). Prior art jacks to my U.S. Pat. No. 5,478,261 mate with the male contact of the plug in an angular orientation of the spring contact of the jack. This results in a poor impedance match between the male contact of the plug and the spring contact of the female because the contacts are not substantially co-aligned with each other. The result of this poor impedance match is an unacceptable reflection of part of the original signal, thus delivering a much weaker signal to the destination. For example, prior art jacks typically have a VSWR of greater than 2.0 with signals transmitted at a frequency of 100 Mbps, while my '5,478,261 jack provides a VSWR of 1.1 at a frequency of 100 Mbps. This means that prior art jacks reflect away more than 33% of the transmitted signal, leaving less than 2/3 of the original signal to continue on to its destination. My '5,478,261 jack reflects away less than 5% of the transmitted signal, providing for more than 95% of the original signal to continue on.
U.S. Pat. No. 5,249,987 illustrates a further improvement to the design of U.S. Pat. No. 5,478,261 by providing a flexible cover located within the upper wall of the jack. This cover is designed to provide a dielectric barrier between the spring contacts and any external electrically charged surface or electrically conductive surface. The cover is made of polymers that have some flexibility in thin sections, thereby providing support for spring contacts which are lifted to a high lift position, and additionally providing for continuing dielectric isolation for the now lifted contacts. The cover will lift in concert with the spring contacts that are lifted such that it lifts equally to those spring contacts which experience the highest lift.
This improved jack still has a disadvantage in that in space limited computers, network boxes, and the like, there is not sufficient headroom above the upper wall of the jack for the spring contacts and the cover to flex to their fully unrestrained position when a smaller position plug is mated and specific contacts are lifted to a high lift position.
While the recent prior art has made significant improvements toward addressing the problem of providing stress resistance of the spring contacts within a modular jack, when those spring contacts are subject to high lift situations as a result of a smaller male plug being mated to a jack, it is towards enhancing the stress resistance of the prior art connectors that the present invention is advanced.